Hi Sebastian
Our client team is currently finishing-off our public API, which we will be publishing in the near future. Once this is out then anyone will be able to write a client for the platform and player of their choice. I run a couple of Linux boxes myself, and I'm hoping to see a healthy ecosystem of third-party clients and plugins for The Filter.
As for our 'official' clients, I'm afraid that a Linux one is not something we have planned for the short term. However, we do constantly assess the market based on user feedback, so you never know.
Cheers,
Dominic, The Filter